AC Filtering, Grounding Boxes, Linear PSU and Balanced Power.

[YashN]

I am building an AC Filtering device which has one inlet, several outlets, each along a filter path. This should help prevent some of the noise re-injected into the mains by some of the switching-mode power supplies from affecting the other components.

 

The design is rather simple:

 

Inlet + Inlet filters -> Rails -> separate Filters for each outlet

 

On researching and building this, however, a lot more questions cropped up not just about the AC Filtering, but about alternate approaches or additional devices, and general use.

 

1. I could use duplex outlets, but if I were to plug two devices in one of these, would one device be well isolated from the second one?

 

2. I believe I'll benefit by plugging the iMac into it, but I think I would need to build a new, properly shielded power cable for it to keep the benefits of the filter box.

 

3. If I plug my amp in the filter box, then the line sees a 'pre-filter' before heading into my amp's power supply. I believe this could potentially be good, but it could also be detrimental to dynamics.

 

4. If I use that filter box, will I still derive cumulative benefits if I install Linear PSUs? I think this is a 'yes'.

 

5. If I use balanced power (like Equi=Tech or an isolation transformer), do I get cumulative benefits with the filter box? With the filter box and LPSUs? Or could the installation of balanced power replace some of this arrangement?

 

6. Currently, in the arrangement for stereo, only the iMac is grounded:

External HDD -> iMac -> DAC -> Amp. Theoretically, this should be OK, but I do hear some high-frequency hash that diminishes timbral accuracy for cymbals and the like, and proves fatiguing in the long term.

 

During my recent readings, I was reminded of the importance of the Ground Plane in DIY Ham radio circuits. In equipment which has not been designed properly, this is not well implemented. Thus, we often find ourselves with a mix or properly and improperly designed equipment, each with their own grounding scheme, each with either a two-prong power cable or a 3-pronged one.

 

Could this be the explanation why some people report getting much better results using grounding boxes? Take for example two commercial products which are very expensive and out of my budget:

 

1. Tripoint Troy - Grounding box used for chassis grounding for all components of your playback chain. This connects through a Ground pin only to mains.

 

2. Entreq Tellus - Autonomous Grounding box initially reserved for grounding Signal returns (e.g. an RCA return from each of your components). This doesn't connect to any other ground or earth, it has its own internal ground.

 

Are our power lines, grounding schemes, power supply units are compromised in various ways and greatly spoiling our enjoyment of music?

[sandyk]

I use 2 heavy duty mains filter in the same case . One for supplying the LED backlighted TV, and the other for my normal audio gear. They are based on a design by Silicon Chip magazine. The only mains rubbish that I get through is due to DTV reception in this low signal area with Rabbit's Ears and a low noise MHA, when the fluoro in the toilet across the hallway gets turned on.

Fortunately, 230V AC 50HZ mains supplies don't appear to normally have problems anywhere near as bad as those with 115V AC 60HZ.

[YashN]

I use 2 heavy duty mains filter in the same case . One for supplying the LED backlighted TV, and the other for my normal audio gear. They are based on a design by Silicon Chip magazine. The only mains rubbish that I get through is due to DTV reception in this low signal area with Rabbit's Ears and a low noise MHA, when the fluoro in the toilet across the hallway gets turned on.

Fortunately, 230V AC 50HZ mains supplies don't appear to normally have problems anywhere near as bad as those with 115V AC 60HZ.

 

Thanks Alex. I think I could go with that type of setup: each outlet line is a separately filtered one, totally passive. The inlet-side rails has a common filtering.

 

For testing, I am restricting myself for now to a simple stereo playback chain.

 

If at one outlet I use a duplex instead do you think I could connect one external HDD and the iMac in there (just as an example) or it would be better than these are on two separate Duplex elements?

 

I do think when I was supplied with Euro-style 220-240V/50Hz the mains was cleaner. But that's before I moved to North America.

[sandyk]

Yashn

Normal mains filters may not be as efficient as a specially designed heavy duty filters that also take into account SMPS rubbish coming back the other way ? SMPS gear such as DVD players etc. do have small mains filters built in, but they are only designed to comply with statutory emission requirements.

 

Alex

[YashN]

Yashn

Normal mains filters may not be as efficient as a specially designed heavy duty filters that also take into account SMPS rubbish coming back the other way ?

 

Certainly, and I'm not trying to compete with commercial offerings here.

 

I'll definitely separate analog and digital and perhaps small power from big power.

 

Since each line in my filter box has its own filter, each component will have less opportunity of affecting the other components.

[Speedskater]

If you are going to make several filters, the best place for a filter is at the component's chassis. With the filter touching the chassis if possible.

 

Dual receptacle's can be split in to two circuits.

 

Lay-out everything in a way to reduce the length of the Safety Ground/Protective Earth wires from component to component to a reasonable minimum.

 

The real experts on this topic are:

Keith Armstrong

Ralph Morrison

Henry W. Ott

But none are easy reading, nor convenient.

 

More accessible are papers by (but they still require some studying) :

Jim Brown

Bill Whitlock

Middle Atlantic

[YashN]

If you are going to make several filters, the best place for a filter is at the component's chassis. With the filter touching the chassis if possible.

 

Thanks Speedskater, saw a few of your cool posts and references over at WBF.

 

That's an interesting idea as well. Do you have any link with an implementation? Do you think this is the same thing that the Tripoint Troy devices do?

 

Dual receptacle's can be split in to two circuits.

 

That would be ideal. Does this necessitates some mechanical work to enable or should I check how the duplexes are implemented? I thought they had common rails for each lead.

 

The real experts on this topic are:

Keith Armstrong

Ralph Morrison

Henry W. Ott

But none are easy reading, nor convenient.

 

Heard about Morrison and Ott: Ott from reading and researching a couple of years ago about ground planes, and recently saw Morrison mentioned as a very accesible read.

 

More accessible are papers by (but they still require some studying) :

Jim Brown

Bill Whitlock

Middle Atlantic

 

I think I have these saved on my HDD for future reading sessions, together with a couple of Ott texts.

[YashN]

I was reading some interesting texts from the Equi=Tech website. They make Balanced Power devices:

 

What is wrong with grounding? The answer is simple. As a rule, the grounding circuit is not meant to carry any type of current except for rare occasions when there is a short circuit, and then only momentarily. However, Underwriters' Laboratories standards are somewhat lax in this respect. “Objectionable ground current" is loosely defined in every area except for hospital operating rooms. Outside of hospitals, “objectionable ground current” is gauged more closely to shock hazard levels (about 3.5 milliamps). It seems that this standard has backfired. Data corruption, disk crashes and simple hum noise cost time and money -- sometimes a lot. Clearly, UL standards that define "objectionable ground current" are inadequate by today's standards. On the other hand, UL is not responsible for re-engineering audio equipment and AC systems. Normally, performance standards are left up to manufacturers and the marketplace. The basic problem is that when loaded, all differential mode 120-volt AC circuits create noise in the ground reference. Noise problems occur in audio signal circuits due to an unclean ground. The old Edison circuit (where a 240-volt circuit is split into two 120-volt circuits) is still used today as a standard means of 120-volt power distribution. Standard power is unbalanced. Even when a high quality 120-volt isolation transformer is installed, one side is grounded (made neutral) which is really not much different at all. The way the AC voltage phase is referenced and carried by the circuit has everything to do with electrical interference in a grounding system. If any aspect of the circuit is applied or loaded in an unbalanced manner, noise will appear in the ground.

 

 

The system was built full of ground loops, but grounding currents and chassis potentials were nowhere to be found. This is how it should be. Star grounding and linear signal reference grids are nothing more than "Band-aids" that, at best, can only marginally mask over some of the noise. To be free of noise problems, grounding circuits must remain clean -- that's all there is to it. If they're not, a hundred ground rods won't help.

[YashN]

Now, the interesting thing is that Equi=Tech mentions that using balanced power resolves the issues.

 

On the other hand, people like spiritofmusic over at WBF have benefited from using the Entreq Signal plane grounding even after using Balanced Power.

[Duke40]

5. If I use balanced power (like Equi=Tech or an isolation transformer), do I get cumulative benefits with the filter box? With the filter box and LPSUs? Or could the installation of balanced power replace some of this arrangement?

 

For my speaker rig I jut use a 3000W Balanced Power Supply, just 2 pieces of gear attached (Integrated amp and a DAC). Neither piece of gear is noisy and the way balanced power works, they can co-exist just fine.

 

For my Headphone rig/home theatre, a bit more complicated.

I find that I get cumalative benefits with the following setup to my DAC/Headphone AMP ;

 

1500W Balanced Power Supply > 300W Isolation Transformer > 100W Linear PSU > DC Reservoir

 

1. Balanced Power Transformer ... this provides the bulk of the benefits, though I plug a TV (SMPS) into it.

2. Isolation Transformer ... outlets not isolated ... even though both devices attached to this isolation transformer use Linear PSU ... one of them (OppoMod PSU) did not have an EMI filter so recently put in a Furutech EMI Filter into the Oppo BDP-103 (though thinking of getting another one which is designed specifically for this Oppo), HD-Plex also attached.

3. Linear PSU ... for Regen, hub

4. DC Reservoir ... not really a real term, not sure what to call it ... just what was mentioned in the TBI OFR-1 manual, attached to the 19V rail of my HD-Plex, to feed my headphone dac/amp. Has 25 Joules of energy.

 

I also use shielded power cables.

 

I found by step 4 the diminishing returns had hit hard as far as sound quality improvements went.

 

If I could just have one type of device it would be the Balanced Power Transformer.

2nd choice would be the Linear PSU.

Others much more knowledgeable than me suggest having the Isolation Transformer before the Balanced Power Supply.

 

Though putting the EMI Filter into the Oppo was worthwhile (the OppoMod Linear PSU that I have does not come with a filter and it was putting some noise back into the Isolation Transformer).

 

I find that once you provide better power to your system ... the next big challenge is to stop each device from adversely affecting each other.

 

Other people posting on this thread are much more knowledgeable than me.

 

Anyway, hope that helps. Have fun & be safe.

[Speedskater]

Many segments of the 850 page Henry W. Ott book "Electromagnetic Compatibility Engineering" are viewable online. If you just skip the math formulas it's vary readable.

EMC Books

 

As for the old Ralph Morrison books, I purchased some of the used, online for $10 to $15 each.

But Mr. Morrison writes in field theory rather than circuit theory. It's hard to transfer field theory to real life.

[Speedskater]

Here is on almost readable Keith Armstrong article. The interesting part is well down the page.

 

"Fundamentals of EMC Design: Our Products Are Trying To Help Us"

 

Author : Keith Armstrong, Cherry Clough Consultants

04/03/2012

 

Fundamentals of EMC Design: Our Products Are Trying To Help Us | Interference Technology

 

****************************************************

This is a Keith Armstrong youtube. But I don't remember watching all of it.

 

[h=1]Understanding EMC Basics Part 3:

Grounding, Immunity, Overviews of Emissions and Immunity,[/h]

 

Fundamentals of EMC Design: Our Products Are Trying To Help Us - See more at: Fundamentals of EMC Design: Our Products Are Trying To Help Us | Interference Technology

Fundamentals of EMC Design: Our Products Are Trying To Help Us - See more at: Fundamentals of EMC Design: Our Products Are Trying To Help Us | Interference Technology

[YashN]

Dual receptacle's can be split in to two circuits.

 

I think this is how, right?

 

[h=2]How To Wire Split Outlets... Step #6: Remove Hot Tab on the Outlet[/h]

 

 

 

 

 

 

Remove the Hot Tab to Split the Outlet. Photo Credit: Timothy Thiele

 

There is a tab on the hot wire connection side of the outlet called the hot tab. Locate the side of the outlet where the brass screws are located. Between the two screws and the face of the outlet, you'll notice a small brass piece of metal (called a tab)connecting the hot feeds. Simply break it off by inserting a screw driver under it and bend it back and forth. You can also use long nosed pliers to break it loose. Once remove, the common bond is broken.

[Jabs1542]

I think this is how, right?

 

Yes, remove the jumper. Notice that each receptacle has its own pair of wiring sockets, so you will now feed it two wire pairs instead of one.

[YashN]

I also use shielded power cables.

 

I found by step 4 the diminishing returns had hit hard as far as sound quality improvements went.

 

If I could just have one type of device it would be the Balanced Power Transformer.

2nd choice would be the Linear PSU.

Others much more knowledgeable than me suggest having the Isolation Transformer before the Balanced Power Supply.

 

I find that once you provide better power to your system ... the next big challenge is to stop each device from adversely affecting each other.

 

I made my own AC cable for the amp using separate shielded single core: it's better than the stock cable.

 

Interesting thought about the iso transformer before the balanced power.

 

As for stopping each device affecting the other, this is precisely what my AC filter is planned for: since each component has its own filter line, it is very difficult for one component to affect another one.

[YashN]

Here is on almost readable Keith Armstrong article. The interesting part is well down the page.

 

"Fundamentals of EMC Design: Our Products Are Trying To Help Us"

 

Thanks for the additional links, Speedskater, very cool info in there.

[YashN]

As it was nearly impossible to solder wires to the previous single plugs I bought, today I got some more normal-looking duplex units: one white duplex, one ivory and one black.

 

I intend to separate the filter lines for analogue, digital and amp/high-current.

 

But even prior to getting the duplex units, we did a really small and incomplete test last night with a single filter line (the two other lines did not hold...).

 

I chose the iMac as the component to connect, and we were both asking ourselves separately and silently at the time "How could this sound even better, I don't see how?".

 

The reasons for these were because I had already floated and tested the speakers as well as the HDD on a ball-and-cup arrangement, to isolate from horizontal vibrations and rotations and we noticed great improvements in soundstage, a reduction of bass bloat, and a clarity in the mid-range up to the very high-frequencies.

 

Knowing that ideally, I should also filter at least the external HDD (right?) and the amp, and that I really should do another cable for the iMac to keep the filter benefits to the max, I wasn't really expecting much.

 

Well, were we both surprised!

 

Even more space in the soundstage, well-defined mid-range, hearing soft rhythms play out, people preparing to play their instruments and involuntarily making sounds when touching them, lips before singing, a holographic effect as if the backing vocalists were in tow arcs in the room, etc...

 

So that great experience prompted me to get the additional hardware to try and finish a complete prototype with at least 3 or 4 lines (normally 6 with the three duplex units that I manage to separate into 6 independent ones, but here I need to check combined amperage).

 

I removed the flaky connections, re-did the new ones with the duplex units and the wires strongly screwed down this time, but hit a couple of snags before finally getting it to work.

 

On listening, we found something really odd: all native DSD recordings were very rolled-off, but Redbook up-converted to DSD128 sounded fine.

 

Took me some time to realise I had accidentally turned my amp to "Front Speakers A - Low Impedance".

 

I though the filter line used was the culprit, but it could be just that impedance mismatch which ruined the test tonight.

 

Hence, tomorrow, in between floating the computer and the DAC properly as well as making a new lighter USB cable, some new listening tests are in order for the filter.

 

Judging by the tests last night, this should be very promising.

[YashN]

1500W Balanced Power Supply > 300W Isolation Transformer > 100W Linear PSU > DC Reservoir

 

1. Balanced Power Transformer ... this provides the bulk of the benefits, though I plug a TV (SMPS) into it.

2. Isolation Transformer ... outlets not isolated ... even though both devices attached to this isolation transformer use Linear PSU ... one of them (OppoMod PSU) did not have an EMI filter so recently put in a Furutech EMI Filter into the Oppo BDP-103 (though thinking of getting another one which is designed specifically for this Oppo), HD-Plex also attached.

3. Linear PSU ... for Regen, hub

4. DC Reservoir ... not really a real term, not sure what to call it ... just what was mentioned in the TBI OFR-1 manual, attached to the 19V rail of my HD-Plex, to feed my headphone dac/amp. Has 25 Joules of energy.

 

I also use shielded power cables.

 

I found by step 4 the diminishing returns had hit hard as far as sound quality improvements went.

 

If I could just have one type of device it would be the Balanced Power Transformer.

2nd choice would be the Linear PSU.

Others much more knowledgeable than me suggest having the Isolation Transformer before the Balanced Power Supply.

 

That was part of my questioning: i.e. if there were overlaps with say the AC filtering and balanced power, and additionally, if I start with Balanced Power, do I really need an isolation transformer as well, and do I also need linear power supply. I wanted to avoid going overboard with several devices when possibly a single more fundamental change would provide 80% of the benefits for 20% of the efforts.

 

But I think your experience echoes a little of what I read by spiritofmusic on the WBF forum (I think he's in UK), that is, large benefits with balanced power, but he additionally found great results in his rig by using the Entreq signal isolation products.

 

Though putting the EMI Filter into the Oppo was worthwhile (the OppoMod Linear PSU that I have does not come with a filter and it was putting some noise back into the Isolation Transformer).

 

I don't know if you've come across Coris and Rasmussen on diyaudio.com: they both have some cool mods for Oppo BDPs.

[4est]

The PS itself is likely the most important aspect. It would seem that some think that simply using a non-smps is the key when output impedance and freq response are typically king. Different power supplies sound different - period. Note that the aforementioned Coris was selling one on diyaudio. If one does not want to pay in cash for say a JS-2, they would be well served to build some and experiment.

That was part of my questioning: i.e. if there were overlaps with say the AC filtering and balanced power, and additionally, if I start with Balanced Power, do I really need an isolation transformer as well, and do I also need linear power supply. I wanted to avoid going overboard with several devices when possibly a single more fundamental change would provide 80% of the benefits for 20% of the efforts.

 

But I think your experience echoes a little of what I read by spiritofmusic on the WBF forum (I think he's in UK), that is, large benefits with balanced power, but he additionally found great results in his rig by using the Entreq signal isolation products.

 

 

 

I don't know if you've come across Coris and Rasmussen on diyaudio.com: they both have some cool mods for Oppo BDPs.

[YashN]

The PS itself is likely the most important aspect.

 

One could also improve each component's PS individually, but I don't have sufficient knowledge yet to go and mod my amp's PS or the iMac's.

 

It would seem that some think that simply using a non-smps is the key when output impedance and freq response are typically king.

 

I think it's really difficult to make an excellent SMPS PSU and these are usually prone to creating a lot of noise or EMI/RFI compared to linear ones.

 

If one does not want to pay in cash for say a JS-2, they would be well served to build some and experiment.

 

One future project would be to build a small linear PSU to experiment with overall sound, perhaps for the DAC, but it already has a battery. If that works, maybe I can even re-build a special USB cable without the power line.

[YashN]

New tests today, making sure the "Low Imp" is turned off.

 

I am using the DAC with the 'Measure' Filter mode. Initially, the sound appeared to still have some roll-off at the top end for native DSD, but it seems to be improving along the day.

 

Another thing we noticed with the AC filter on the iMac is that when using Display Mirroring on the HDTV, the screen is clearer: the fonts more defined. Fun.

[YashN]

In the stereo setup, I have the external HDD (one, and sometimes two), the iMac and the amp, and perhaps later the turntable and the Tube Amp (it already has its own filter).

 

It is said to be necessary to separate digital and analogue, and separate high-current from low-current, so I think I could put the HDD and the iMac at one end of the distribution, and the amp at the other extreme. Is considering the HDD as 'digital' the correct way here?

 

For now, only one filter line is active.

 

For surround, I will have another sound card (external USB), one active subwoofer, and one active centre channel.

 

That makes two additional amps, so I think I might need another AC filter box rather than put all these within my first one.

 

Further down the line, I may need one for the TV, Apple TV and Blu-Ray too.

[One and a half]

I made my own AC cable for the amp using separate shielded single core: it's better than the stock cable.

 

Interesting thought about the iso transformer before the balanced power.

 

As for stopping each device affecting the other, this is precisely what my AC filter is planned for: since each component has its own filter line, it is very difficult for one component to affect another one.

 

Using the Isolation transformer in front of the Balanced power transformer does two things.

 

1. To slow the current peaks from the balanced transformer primary, so it acts like a choke.

2. Provide some soft starting for the balanced transformer.

 

There is no overlap, the isolation transformer and balanced transformer do different jobs.

 

If you had to choose and just use the one device, the balanced transformer would be it. Depending on how much rubbish there is on the secondary of the balanced transformer, this out of balance rubbish has to go somewhere, and ends up in the primary windings as an acoustic noise.

 

Use of an isolation transformer connected upstream of an Equitech transformer is a recommended practice from Equitech.

 

I found the use of a standard line conditioner in front of the Equitech restricted the dynamics and made the bass almost non existent. Would not recommend to use this device. Downstream is also a problem, since it regards the Equitech balanced supply as a fault although the filtering does work better on a balanced supply (if it uses a typical T filter).

 

To avoid cross contamination between components is not that simple, since an audio component will provide a different spectrum. The injection mains side spectrum from an amplifier is different to a CD player or computer, so the filter should be tuned individually. You can add standard EMC filters PLUS use the balanced supply, since the filters work better on a symmetrical supply, rather than one side grounded if you still wanted to keep the filters.

The balanced transformer does a great job of providing an effective cross pollution from other components on its own. Having several filters in parallel could cause a surprise in that there could be a resonance condition, but not likely.

[Duke40]

The PS itself is likely the most important aspect. It would seem that some think that simply using a non-smps is the key when output impedance and freq response are typically king. Different power supplies sound different - period. Note that the aforementioned Coris was selling one on diyaudio. If one does not want to pay in cash for say a JS-2, they would be well served to build some and experiment.

 

Forrest, Thank you. Well, the bit I highlighted, uh, that would be me, so I am guilty of this.

Though I am still trying to learn & understand how all optimising power works, so I do appreciate your comments.

 

Contacted a French electrical engineer who makes a line purifier that can work with the OppoMod.

 

Funny timing that both YashN and you mention Coris on diyaudio.com ... I am still working thru that thread, I am interested in the PSU that Coris designed.

 

@ YashN ...Will check out Rasmussen (at least he is local, believe Sydney based) though I believe he focus on clocks for the Oppo (which is another current interest of mine, still trying to work out if it is worth it). He seems a bit more expensive, though his modded oppo's do seem to get snapped up very quickly on the local market.

[4est]

I am sorry if I seemed testy or pedantic. I also have no desire to point fingers. Essentially what I was attempting to say is that some linear PSs sound like crap for various reasons. No amount of power conditioning will ameliorate these issues. In particular, some older 3 terminal type regulators (lm317, 78xx) just aren't up to the task. Those are often seen in inexpensive power supplies for their simplicity.

 

I mentioned Coris because YashN had. I have respect for Joe Rassmussen, and use a variation of his suggested transformer I/V for my saber based DAC. It completely and utterly smokes the supplier suggested versions.

Forrest, Thank you. Well, the bit I highlighted, uh, that would be me, so I am guilty of this.

Though I am still trying to learn & understand how all optimising power works, so I do appreciate your comments.

 

Contacted a French electrical engineer who makes a line purifier that can work with the OppoMod.

 

Funny timing that both YashN and you mention Coris on diyaudio.com ... I am still working thru that thread, I am interested in the PSU that Coris designed.

 

@ YashN ...Will check out Rasmussen (at least he is local, believe Sydney based) though I believe he focus on clocks for the Oppo (which is another current interest of mine, still trying to work out if it is worth it). He seems a bit more expensive, though his modded oppo's do seem to get snapped up very quickly on the local market.